Brazed plate heat exchangers are commonly used for oil coolers and to a lesser extent are known for use in refrigeration systems. Because of their compactness, such heat exchangers are desirable for use in systems having a limited installation envelope, such as in vehicular applications. One drawback to conventional brazed plate heat exchangers is that their construction does not lend itself to high pressure applications where, for example, the operating pressures can be 1000 psi to 2000 psi or greater and the burst pressure requirements can be in the range of around 4000 psi to around 6000 psi. In this regard, conventional brazed plate heat exchangers are typically limited to less than 1000 psi. This has prevented the use of such heat exchangers in high pressure systems, such as for example, transcritical cooling systems that use a refrigerant such as carbon dioxide (CO2).
Increasing environmental concerns over the use of many conventional refrigerants such as CFCl2 and, to a lesser extent HFC134a, has led to consideration of transcritical CO2 systems for use in vehicular applications, heat pumps, water heaters, and refrigeration systems. For one, the CO2 utilized as a refrigerant in such systems could be claimed from the atmosphere or from waste products of other industrial processes at the outset with the result that if it were to leak from the system back to the atmosphere, there would be no net increase in atmospheric CO2 content. Moreover, while CO2 is undesirable from the standpoint of a greenhouse effect, it does not affect the ozone layer and would not cause an increase in the greenhouse effect since there would be no net increase in the atmospheric CO2 content as a result of the leakage.